Devices and methods for examining the properties and conditions of display devices are known in the art. Generally, these devices, such as colorimeters, are placed in close proximity to the screen of the display device and utilize a sensor to analyze the light characteristics emitted by the display screen, such as the color. However, to obtain the most accurate measurement of the light emitted by the display screen, the sensor should be positioned to directly observe pixels comprising a defined target area of the display. This means receiving light into the colorimeter that is along the normal to the display screen (such light being called on-axis light, and other light being called off-axis light). For a liquid-crystal display (LCD), light is emitted at all viewing angles so that a colorimeter with a non-selective viewing geometry will observe light that is not completely correlated with the directly-viewed light from the picture elements (pixels). As an example of this phenomenon, when LCDs are viewed off axis, lighter colors are produced when the display is commanded to produce dark colors.
Thus, off-axis light alters the measurements of a light sensing device by producing a higher recorded light value than can be attributed to the light emitted by the directly observed pixels. To correct this false positive, prior art solutions focus on preventing off-axis light from reaching the light sensor. For example, U.S. Pat. No. 6,784,995 describes using a black baffle with narrow holes to conduct only light in a selected direction so as to reduce off-axis light contamination. Alternatively, X-Rite's I1 Display Pro®, manufactured by X-Rite of Grand Rapids, Mich., diminishes off-axis light by introducing a lens that conducts light only from a preferred direction.
However, in both of these examples, additional hardware is needed to reduce the influence of off-axial light on the measurements. Thus, what is needed is a system and method to reduce off-axis light when measuring the light characteristics of a display without requiring additional hardware in the light sensor.